Previewed at WWDC, launching in the fall.
Mac OS X 10.6 to Drop PowerPC Support?
Looking ahead, those people familiar with Apple development cycles speculate that Mac OS X 10.6 will exclude support for PowerPC-based Macs entirely, requiring that users have one of the company's Intel-based systems which first began making their way to market in early 2006.
Cited as speculation, Apple may not yet have made a decision on this matter. Apple has made no announcements about Mac OS X 10.6. Based on the most recent Mac OS development cycles, Mac OS X 10.6 would not likely ship until 2009.